There is a wide array of technologies directed to in vivo and ex vivo imaging of mammals—for example, optical (e.g. bioluminescence and/or fluorescence), X-ray computed tomography, and multimodal imaging technologies. In vivo imaging of small mammals and ex vivo imaging of samples from small mammals is performed by a large community of investigators in various fields, e.g., oncology, infectious disease, and drug discovery.
Micro computed tomography (hereafter, “microCT”) imaging, is an x-ray-based technology that can image tissues, organs, and non-organic structures with an extremely high resolution. MicroCT has evolved quickly, requiring low dose scanning and fast imaging protocols to facilitate multi-modal applications and enable longitudinal experimental models. Similarly, nano-computed tomography (nanoCT) systems designed for high-resolution imaging of ex vivo samples are also now used. Multi-modal imaging involves the fusion of images obtained in different ways, for example, by combining fluorescence molecular tomography (FMT), PET, MRI, CT, and/or SPECT imaging data.
Multimodal imaging allows improved visualization of disease biology, e.g., for use in drug development and diagnostics. By utilizing in vivo bioluminescent and fluorescent agents and/or radioactive probes, researchers can measure depth, volume, concentration, and metabolic activity, facilitating medical research. Coregistration allows researchers to overlay images from multiple imaging modalities, providing more comprehensive insight into the molecular and anatomical features of a model subject. For example, optical imaging data can be used to identify and quantify tumor burden at the molecular level and, when integrated with microCT, provides a quantitative 3D view of anatomical and functional readouts.
Various systems have been developed that allow accurate multimodal imaging. For example, various IVIS® in vivo imaging systems, manufactured by PerkinElmer headquartered in Waltham, Mass., feature a stable revolving animal platform (horizontal gantry motion with flat panel detector) for acquisition of 3D data, facilitating low-dose imaging and automated optical and micro-CT integration. Such systems provide 3D tomography for bioluminescent and fluorescent reporters, enhanced spectral unmixing for multispectral imaging, Cerenkov imaging for optical radiotracer imaging, and dynamic enhanced imaging for real time distribution studies of fluorochromes and/or PET tracers, e.g., for pharmacokinetic/pharmacodynamics PK/PD modeling.
Conventional computed tomography (CT) imaging systems may require higher-than-desirable radiation doses to obtain satisfactory reconstructed images and may pose challenging memory management problems. CT image reconstruction from multiple projections is computationally intensive. CT image reconstruction generally involves obtaining a sinogram, which is a multi-dimensional array of data containing projections from a scanned object (e.g., projections recorded for a plurality of angles during multi-angle scanning of an object).
Artifacts arise when imaging objects that are too large to fit into the physical beam of a given system, or when the object is too large for a given reconstruction field of view (FOV) due to memory or data storage limitations. Furthermore, it is often desirable to reduce radiation dose by only exposing a particular area of interest. However, such situations result in sinogram data truncation which must be “filled in” to permit reconstruction. No adequate solutions have been proposed for automated sinogram completion in a multi-modality approach.
Thus, there is a need for systems and methods for automated completion of a truncated sinogram to permit satisfactory image reconstruction and coregistration/combination with optical images.